Forum ‹ C# ‹ Lock and List Question.

[FulaFisken]

We have this issue in our code. My question is, can it happen because we have the return statement outside of the lock? Or do we have problem elsewhere? We have locked all code snippets that add or remove from the list with the unitListLock object.

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Collection was modified; enumeration operation may not execute.
First seen 18 hours ago, latest 43 minutes ago. (Delete 2 errors)

   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   at System.Collections.Generic.List`1.Enumerator.MoveNext()

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private Unit FindNearestInRangeTarget()
{
  Unit nearestTarget = null;
  lock (g.unitManager.unitListLock)
  {
      foreach (Unit u in g.unitManager.units)
      {
         SetNearestTarget(u, nearestTarget, out nearestTarget);
      }
   }
   return nearestTarget;
}


[Mrx3D]

HEy, And you are also locking on the same object, when adding or removing "Unites" from the list?

[FulaFisken]

Yes, we do lock the same object while removing, and adding.

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public void Remove(Unit unit)
{
    lock (unitListLock)
    {
        units.Remove(unit);
    }
}

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[MethodImpl(MethodImplOptions.Synchronized)]
public void Add(Unit unit)
{
    lock (unitListLock)
    {
        id++;
        if (unit.Id != 0)
           g.PlayerIO.ErrorLog.WriteError("ERROR: UnitId already in use. Lock doesn't work.");

        unit.Id = id;
        units.Add(unit);
    }
}

Thank you for the reply!

[Mrx3D]

The "[MethodImpl(MethodImplOptions.Synchronized)]" attribute might be messing with your lock's, I'm not sure as i have never used that attribute with lock's

[FulaFisken]

The "[MethodImpl(MethodImplOptions.Synchronized)]" attribute might be messing with your lock's, I'm not sure as i have never used that attribute with lock's

If we remove that it gets much worse. I don't know why, but it looks like id++ is iterated within lock(unitListLock) if we don't synch the whole method.